1. Field of the Invention:
This invention relates to the field of pneumatic type tires for vehicles such as automobiles, trucks, cycles, etc., and is more particularly directed to an improved design for a composite cellular insert to be placed inside pneumatic type tires to provide a pneumatic tire with the ability to sustain punctures without resulting in a detrimental loss of compressed air from within the pneumatic tire.
2. Description of the Prior Art:
The pneumatic tire has existed since 1846 when inventor Robert Thompson received a patent for his "Aerial Wheels". And ever since its invention in 1846 to the present date, if pneumatic tires are punctured, they go flat. Therefore, a need has long existed for an apparatus that would eliminate losing the entire volume of compressed air from within a pneumatic tire when its punctured. A great number of apparatuses have been proposed to solve this problem. Efforts as most recently as U.S. Pat. No. 4,416,844 to Wyman, Nov.22, 1983 to as far back as 1892 in U.S. Pat. No. 488,061 granted to Bunker, have tried to solve the problem of pneumatic tires going flat. However, drawbacks have negated all previous "flat-proofing" apparatuses and over-the-road tires today are subject to flats and dangerous high speed blow-outs, just as they were when pneumatic tires were first utilized.
The reason the apparatuses of the prior art have failed to provide a functional means of "flat-proofing" modern over-the-road pneumatic tires is because they do not contain the required volume of pressurized air and they are too heavy. These two key elements are essential for the proper function of pneumatic tires. The larger the volume of air translates into lower required pressure to support the same load. This lower pressure results in a dramatic increase in the tire's ability to absorb bumps and other road irregularities, and not transmit them to the chassis. The weight of a flat-proofing apparatus directly affects unsprung weight. Unsprung weight is any part of an automobile not mounted directly to the chassis. The tires, wheels and any flat-proofing apparatus inside the tire, are all 100% unsprung weight. It has long been known that unsprung weight should be kept to an absolute minimum. These critical elements of high air volume, i.e. low pressure, and low unsprung weight have been known in the art for the past 65 years. Herbert Chase in AUTOMOTIVE INDUSTRIES, Vol. 48, April 12, 1923, p.812-814, discusses the importance and benefits of high air volume and low unsprung weight for pneumatic tires. Fred Duesenberg in THE JOURNAL of the SOCIETY of AUTOMOTIVE ENGINEERS, Vol. XII No. 6, June 1923, p.616-617, also stresses the importance of keeping unsprung weight to an absolute minimum. These references clearly establish 65 years ago, that maximum air volume and absolute minimum unsprung weight have benefits that should be strived for. And which are now essential to the modern automobile. A flat-proofing apparatus must emulate these elements.
Efforts to obtain a flat-proof tire by filling the air chamber of of a pneumatic tire and wheel rim assembly with a closed cell, elastomeric foam produced by a chemical reaction inside the tire, are described in U.S. Pat. No. 3,022,810 to Lambe, Feb. 27, 1962 while the foam density envisioned by Lambe was of the order of 5-10 pounds per cubic foot, it has been established that the actual foam density required to achieve the equivalent pneumatic pressure is 6 times the density postulated. Chemically foamed elastomer tire fillings generated in situ, have the following problems: (1) they increase the unsprung weight to an unacceptable level, (2) continued operation at speeds above 35 MPH causes the foam to generate heat, due to flexing (hysteresis), which at 60 MPH reaches 400 degrees F. causing the foam to revert to a liquid, (3) excessive tire deflection causes the foam to "crumble". These and other problems with chemically foamed elastomer tire fillings for over-the-road use are well known in the tire industry. A paper by J. S. Hawkes, of Goodyear Tire & Rubber Co., titled "FOAM INFLATED TIRES", published in the June 1970 issue of RUBBER AGE Magazine, p. 47-53, documents these problems. These problems appear to be insurmountable in view of the fact that over the past 20 years Goodyear, nor anyone else in the art, has perfected a chemically foamed tire filling free of the aforementioned problems. As evident by the fact that no chemically foamed pneumatic tire filling is commercially available for public highway use, nor Department of Transportation approved for public highway use. This can be attributed to structural and other characteristic of closed cell flexible foams produced directly from a chemical reaction. Namely, cell sizes approximately 0.080 of an inch, cells elongate in the direction of foaming, "ribs" form where cell walls join, reduction in cell wall thickness due to drainage and capillary action, extremely low tensile strengths and difficulty in obtaining a specific cell gas pressure.
Efforts to obtain a flat-proof pneumatic tire also consist of concepts utilizing an array of preconstructed, pressurized, flexible, spherical cells inside a tire and to join the spherical cells into a single mass by using a substantial amount of matrix filler material between the spherical cells. In this way, if some cells were punctured, the remaining cells and matrix filler material would prevent the tire from becoming flat. Examples of this concept are embodied in U.S. Pat. No. 1,449,588 to Connolly, Mar. 27, 1923 and British Patent 11,504 to Wolken, Aug. 9, 1915. While each of these patents generally discloses the concept of spherical cells in a tire, the embodiments disclosed therein utilize two-piece or other such cells comprising a substantial cell wall mass and a substantial amount of matrix filler material, such as rubber, between the multiplicity of spherical cells. This substantially reduces the air volume contained in the pneumatic tire and substantially increasing unsprung weight. These two problems render these concepts unacceptable for use in the pneumatic tires of today's modern automobiles.
In U.S. Pat. No. 4,003,419 to Verdier, Assignee Michelin Tire Co., Jan. 18, 1977, he states the main drawback to devices (to flat-proof) inside the tire cavity is weight. In U.S. Pat. No. 3,866,652 to Ahmad, Assignee B.F. Goodrich Co., Feb. 18, 1975, he also states large increases in tire weight are undesirable. And yet the embodiments of the prior art still produce such heavy structures that they are unapplicable for use in today's modern tires on today's automobiles.
Thus, the prior art has not produced a functional apparatus that embodies a high volume of compressed air while at the same time provide a pneumatic tire with the ability to sustain punctures and not be detrimentally effected by the resulting loss of compressed air and not increase the unsprung weight of the tire and wheel rim assembly to a level that renders it useless for commercial over-the-road applications.